package org.apache.commons.graph.builder

/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements.  See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership.  The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License.  You may obtain a copy of the License at
*
*   http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.  See the License for the
* specific language governing permissions and limitations
* under the License.
*/

/**
 * TODO fill me!!
 *
 * @param <V> the Graph vertices type
 * @param <E> the Graph edges type
</E></V> */
abstract class AbstractGraphConnection<V, E> : GraphConnection<V, E>,GraphConnector<V,E> {

    private var connector: GraphConnector<V, E>? = null

    /**
     * Adds a new edge to graph connector.
     *
     * @param <A> the Graph edges type
     * @param arc the edge to add.
     * @return the [HeadVertexConnector]
    </A> */
    override fun <A : E> addEdge(arc: A): HeadVertexConnector<V, E> {
        return connector!!.addEdge<A>(arc)
    }

    /**
     * Adds a new vertex to graph connector.
     *
     * @param <N> the Graph vertex type
     * @param node the vertex to add
     * @return the vertex added
    </N> */
    override fun <N : V> addVertex(node: N): N {
        return connector!!.addVertex<N>(node)
    }

    /**
     * Connects the graph.
     */
    abstract fun connect()

    /**
     * {@inheritDoc}
     */
    override fun connect(connector: GraphConnector<V, E>) {
        require(this.connector == null){ "Re-entry not allowed!"}

        this.connector = connector

        try {
            connect()
        } finally {
            this.connector = null
        }
    }

}
